Process of making ammonia from calcium cyanamid.



- making ammonia action of steam.

cyanamid' further transformed part of it UNITED sTA' Es PATENT OFFICE.

\VALTER S. LANDIS, OF NIAGARA FALLS, YORK, ASSIGNOR T0 AMERICAN CYANAMID COIVIPANY, OE NASHVILLE, TENNESSEE, A CORPORATION OF MAINE.

PROCESS OF i'lIA KING AMMONIA'FROM CALCIUM CYANAMID;

No Drawing. Original application filed February 4,

Specification of Letters fatent.

Patented Dec. 7, 1915.

1915, Serial No. 6,167. Divided and this application filed August 16, 1915, Serial No. 45,810.

To all whom it may concern:

newand useful Improvements in Processes of Making Ammonia from Calcium Cyanamid;

and I do hereby declare the following to be a full, clear, and exact description of the' invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a process for from crude calcium cyanamid, or lime nitrogen, and has for its object to attain this result in a manner more expeditious and less costly than has hereto fore been proposed. 4

llr'ith these and other objects in view the invention consists in the novel steps and combinations of steps constituting my procass, all as will be more fully hereinafter disclosed and particularly pointed out in the claims. This application-is a division of my copending application No. 6l67', filed Feb, 4th, 1915 entitled'Proces's of producin amnio nia',' .now Patent 11-54640, dated ept. 28, 1915.

Inorider that invention may be clearly understood it is said: In the manufacture of ammonia. from crude calcium cyanamid, or'

lime nitrogen, according to the reaction (:aCN,+3T,0:()aCo,+2i Iii the operation was early caiiried out by piling hriqueted calcium cyanamid on trays in a closed apparatus and subjecting this to the But this involved much preliminary tr atment of the crude cyanamid or lime nitrogen, and very great trouble in charging and discharging the decomposition apparatus. The operation of'hriqueting the into other compounds which did not readily yield up, their content of nitrogen in the form of ammonia, and the process was therefore found to be very expensive because of its complexity and. its low yields.

Av later develo'pnient consisted in putting lime nitrogen, or crude calcium cyanamid into an ordinary closed vessel, or boiler, and heating'the same with water, boiling, oil the ammonia in the form of a gas mixed with steam, and running out the remainingrsludge from the containing vessel. But in this case also'it was found very di-flicult to insure a thorough cleaningof the retaining vessel,

for the latter'gradually built up with a hard shell of calcium'carbonate which gave great diliiculty in removal Subsequently,1thisapparatus was changedin themanner of operations'o that water was 'fed into the-same,

then the crude oyanamid, or lime nitrogen, and steam wasinjected into the mass tokeep itstirred up,'a'nd to supply heat; thus preventing it settling on the sides and bottom. This involved, however, the continuous"use o' fst'eam during the 'whole-course of the operation and while tlief operation in part" avoided the difficulties previously-met with,

yet it used, up unnecessarily large-quantities of, steam. Accordingv to my proce'ss-on 'the other hand -I avoid this waste of steam, and

make other changes in the priorprocesses as will ow be disclosed.

" I take advantage of the fact incarrying out my processthat the above reaction is strongly exothermic, and therefore am enabled .to use the steam for a'short time only, .or I may use it intermittently, or' I, after attaining a reacting temperature by any suitable means,- may use it continuously in a greatlydiminished quantity; I IfI use the steam continuously,- 'it may be supplied in a very small stream, and therefore in a much less quantity than has heretofore been [deemed possible. In fact, I have discovered that .it -is only necessary to heat the reacting :mass by any suitable means to'a comparatively low temperature, or to a temperature fisufhcient to start the reaction, when the heat generated by the reaction, will carry it, as far as desired, or to completion; the mass being preferably subjected in the meantime to the steam or'othor heating agent at suitable intervals.

tain periods of the operation, sothat with the aid of the exothermically generated heat the reacting temperature is maintained. I

But of course, as above ;=stated.-the heatmay heCOlltllHlOIlSly applied 7. to said mass in lesser quantities during ccrplosion.

I is.

In my copeuding application, No. 7413,

filed Feb. 10, 1915, and entitled Apparatus the stirring apparatus rotating, and let into my vessel a predetermined quantity of'crude lime nitrogen or calcium cyanamid preferably more or less finely ground. I prefer a comparatively coarsely ground cyanamid as compared to the usual grades used in direct fertilizer applications, for this drops slowly through the feed opening and on striking the water,'or liquor in the vessel, or the spray mentioned in my said co-pending application, it evolves acetylene, from the calcium carbid contained in the said cyanamid, while owing to the free lime 30' present, it slowly, hydrates. I remove the evolved acetylene by sweeping it out of the vacant space in the top of the apparatus with a suitable current of air, or other diluting gas such for example as flue gas, etc., so as to avoid any possibility of the accumulation of the acetylene and its accidental ex- I use such a proportion of lime nitrogen and liquor as will ordinarily yield a rather thin slurry in the apparatus, 6. g. 2 parts by weight of liquor 'to-one part of solids so that thev stirrer Will work through the mixture without undue resistance.

After the charging is complete I close all openings of the autoclave, and preferably introduce steam into the slurry until the manometer on the apparatus shows from say two to four atmospheres of pressures. This produces a temperature sufficient to start the reaction, andI then preferably close the steam inlet so as to cut off the steam entirely or I may almost close the same and employ only a small jet. A fairly rapid increase in pressure occurs in the apparatus when the reaction starts, due to the generation of ammonia, and in from 30 minutes to 1 hour, if all the valves are kept closed, pressures of above 25 atmospheres may be readily attained, depending upon the charge, the size of the apparatus, and how full it I may control these pressures so as to keep them within reasonable limits, either by discharging part of the gaseous contents, of the autoclave, after the steam is shut off, or by properly proportioni'ng the amount of charge used to the size of the apparatus,

operation of admitting steam for a short 7 period of time until a predetermined pres-' sure is attained, when I again blow off the ammonia boiled out of the slurry, together with any that may be formed from an imperfect decomposition of the charge during the first steaming. I may even repeat this operation for a third time, to assure the decomposition of all the cyanamid and to further remove all the dissolved ammonia.

In order to insure practically all the ammonia being driven out of solution in the slurry, I may finally admit'compressed air through the steam inlet, or through another similar inlet, that may be especially pro vided for this purpose, and thus displace the dissolved ammonia completely in a few minutes. I may next discharge the contents of the apparatus through a discharge valve on the bottom, to a filter, thus separating the hot liquor frofn the solids, which liquor I send back into the apparatus for starting a new charge, and thus conserve its heat content and further cut down the steam consumption. Any ordinary type of filter, such as a vacuum-leaf, a pressure-leaf, or a plate and frame type is fourid to be satisfactory,

but I prefer a horizontal vacuum leaf type of filter for this purpose.

In a large apparatus capable of-receiving four tons of crude cyanamid, or lime nitrogen, at one charge, I find thatjn the Whole cycle of operations of filling, decomposing and discharging, covering a period of about ten hours, L need only introduce steam in periods of about fifteen minutes each, and that three such periods yield an efficiency of 99 per cent. in the transformation of cyanamid nitrogen into ammonia.- These results are shown by records over periods of several months runningj and this efficiency is even exceeded Where the filtration step is employed and the liquors returned to the apparatus in the cyclical process,

If steam is used one would naturally ex-. pect a condensation of the same in the ap, paratus, and, therefore, an increase in the bulk of the liquor during theoperation. But I have found out that by the use of superheated steam I can actually cause an evaporation in my apparatus, and, therefore, can subject my filter cakes to a proper washing without apcumulating an excessive amount of liquor for return to the process. 

